BitTorrent "hubs" that publish lists of movies, TV shows and other free downloads suddenly went dark this weekend, in a major victory for Hollywood that highlights vulnerabilities in technology behind the world's busiest peer-to-peer network.

Last week, the Motion Picture Association of America launched a series of worldwide legal actions, aimed at people who ran the infrastructure for BitTorrent networks being used to distribute movies and other copyrighted materials without permission.

The MPAA's actions have put pressure on a short list of large Web sites that had served as hubs for the BitTorrent community and that had operated for months or even years. Many of those sites have now vanished almost overnight, including the SuprNova.org site that was by far the most popular gathering point for the community, serving more than a million people a day, according to one academic study.

News.context

What's new:
Many of the Web sites that served as hubs for BitTorrent file seekers have gone dark, including SuprNova.org, which was the most popular gathering point.

Bottom line: The loss of the big sites is unlikely to eliminate BitTorrent swapping altogether, but it does bring to a close an era of operating in the open without fear of legal reprisals.

The disappearance of the big sites is unlikely to eliminate BitTorrent swapping altogether, but it does bring to a close an era of operating in the open without fear of legal reprisals. The resulting shift to the underground will likely make files harder to find, as traders move onto private networks or smaller communities, file-swapping insiders said.

"We do not know if SuprNova is going to return, but it is certainly not going to be hosting any more torrent links" to content, said a message posted over the weekend to the SuprNova site, which was no longer available Monday morning. "We are very sorry for this, but there was no other way, we have tried everything."

The fallout marks a substantial victory for the MPAA and its allies, which have sat on the sidelines for years as sites such as SuprNova openly set up shop as file-swapping indexes. Such locales became convenient if not indispensable destinations for millions of people seeking one-click downloads of TV shows, movies, games and music.

Over the past two years, BitTorrent has risen to become one of the most popular file-swapping tools on the Net, accounting for a majority of peer-to-peer traffic on ISP networks as of last summer, according
to network monitoring firm CacheLogic. Because the technology was designed from the beginning to make distributing large files

efficient, much of this traffic was dedicated to full-length,
high-quality movies and software.

Nevertheless, the creator of the technology, Bram Cohen, said he's not surprised at the latest developments. BitTorrent was
always designed
for efficient distribution of big files, not underground file-swapping that has to keep a step ahead of the law, he said. Some of the same features that made it useful have rendered it deeply susceptible to the overnight crisis in which the file traders have now found themselves.

"It's weird that it hasn't happened sooner," Cohen said. "The main reason warez (a slang term for illegally distributed software) has become so big is that it hasn't been cracked down on. They've been getting away with being pretty flagrant."

BitTorrent's strength is Achilles heel
Although often mentioned in the same breath as Kazaa or eDonkey, two popular post-Napster file-swapping networks, BitTorrent is actually a very different tool.

Other leading peer-to-peer services aimed to create shifting networks of computers linked over the Internet, in which people could search for specific files and download them from other people's hard drives.

Early versions such as Napster funneled all the searches through a central server, making them relatively easy for groups like the recording industry or the MPAA to shut down. Shutting the central server down through lawsuits or other means would kill the entire network.

"It's weird that it hasn't happened sooner...The main reason warez has become so big is that it hasn't been cracked down on."

--Bram Cohen, creator of BitTorrent

Newer file-swapping networks such as Kazaa, eDonkey and Gnutella are decentralized, without any central point, however. Searches are relayed through the network by individual users' computers. Taking out any of these points has no significant effect on the network as a whole. This makes them much harder to shut down.

Cohen's creation was built around a significantly different model. Each single file is essentially a separate network, controlled by a special "tracker" server that contains all the information about the file itself, where it's located, and who is uploading or downloading it at any given time.

In order to become part of this network, a user has to download a "torrent" file that includes all the information about the requested content and instructions on how to find the tracker server. These torrent files are typically posted on Web sites or distributed through chat services like Internet Relay Chat

Once the torrent is activated, a user becomes part of that file's network, simultaneously downloading bits of the file and uploading them to others once they've been received. This two-way "swarming" traffic makes for fast file-swaps compared with earlier generations of download tools.

However, Web sites like SuprNova and others that operated
the tracker servers were easy targets for the MPAA and its allies in law enforcement. Several other large sites that served as distributors for torrent files, including Youceff.com and Torrentbits.org, also have vanished.

Hollywood officials said last week that legal actions had already been filed against BitTorrent tracker operators in several countries and that they would continue to pursue other copyright infringers online.

"Our message is this: If you are running an infringing server, stop," John Malcolm, the MPAA's director of worldwide antipiracy operations, said last week. "There are more enriching ways to use your talents. Take down your servers immediately, or face the consequences."

The future of BitTorrent
None of this means that BitTorrent is going away. The technology is already widely used in legal ways, such as to distribute games and versions of the Linux operating system. It saves the content publishers considerable money in bandwidth by deputizing their own customers to help in the distribution process.

"I think SuprNova was critical to BitTorrent, but it will still survive."

--Chris Hedgecock, president, Zeropaid.com

Some online tinkerers have been working on ways to merge BitTorrent with the RSS (Really Simple Syndication) news feed technology to create new ways to distribute audio and video. Cohen said he's close to releasing a new version of the technology with some improvements and is spending most of his time looking for ways to make it more mainstream.

SuprNova organizers have been working on a more decentralized version of BitTorrent called Exeem, according to peer-to-peer news site Slyck.com. No word on that project was available after the site's closure.

There's no question that the disappearance of SuprNova and others will be felt widely around the Net, but file-swapping community insiders said it won't dramatically change behavior.

"I think SuprNova was critical to BitTorrent, but it will still survive," said Chris Hedgecock, president of file-swapping community site Zeropaid.com. "It's like Napster was critical to the P2P community. Both sides will continue to evolve."

Indeed, just as in the loss of the original Napster, file swappers themselves are bemoaning the disappearance of what they say was a valuable resource, but they're also already going to alternatives.

"Overall, I think it seems a bit more symbolic," one SuprNova visitor who went by the name "StorDuff" said in an Internet chat interview. He asked that his real name not be used. "SuprNova was highly used and had a huge amount of files, but compared to other torrent sites and P2P networks in general, I don't think its loss will make obtaining or sharing files any harder."